We are investigating polymorphic genetic markers on lymphocytes which are encoded by the midportion of the short arm of human chromosome 6: HLA-A,B,C,D,DR, GLO and complement polymorphisms (Bf, C2 and C4). Genotyping recombinant families have shown that the D, DR, Bf, C2 and C4 are mapped between B and GLO. We will genotype more HLA-D and GLO recombinant families in an attempt to idenfity the gene order of complement, HLA-D. These markers are also important to study C2 and C4 deficiencies. For example, C2 deficiencies are linked to A25, B18, DR2, C4A4, C4A2. We will use these genetic markers to study diseases: juvenile onset diabetes mellitus, 21 hydroxylase deficiency and Kawasaki's disease. We are also investigating newly discovered genetic systems: HT and TL which are expressed on T lymphocytes and have discovered molecular heterogeneity in the human class II molecules (Ia). We have characterized 4 monoclonal anti-p29,34 antibodies, 3 of which immunoprecipitate different molecules. These antibodies can be used as probes to classify different alloantibodies against determinants on B lymphocytes.